Abswurmbachite
Chemical formula: Cu<sup>2+</sup>Mn<sup>3+</sup><sub>6</sub>O<sub>8</sub>(SiO<sub>4</sub>)
Abswurmbachite is a very rare, black copper and manganese mineral from the silicate group, found in metamorphic rocks.
Properties
- Mohs hardness
- 6.5
- Luster
- Submetallic
- Streak
- Black
- Density
- 4.96
- Cleavage
- Indistinct on {110}
- Transparency
- Opaque
- Crystal system
- Tetragonal
Diagnostic features
## Identification Identification of abswurmbachite based on visual characteristics is impossible. Its black color, submetallic luster, and occurrence in a specific metamorphic environment are clues, but certain identification requires advanced analytical methods, such as X-ray diffraction (XRD) or electron microprobe analysis (EDS). ## Distinguishing from Similar Minerals It is visually indistinguishable from braunite, with which it often coexists and is closely related. It can also be confused with other black manganese oxides, such as hollandite or pyrolusite. Differentiation is only possible based on chemical and structural analysis. ## Crystal Forms It most often occurs as irregular, anhedral grains smaller than 0.2 mm. Rarely, it forms aggregates or poorly developed, small crystals with a dipyramidal habit.
Geological environment
## Genesis Abswurmbachite forms under conditions of glaucophane-facies metamorphism (high pressure, low temperature). It forms in manganese- and silica-rich sedimentary rocks that have undergone alteration. It is a rock-forming mineral in some piemontite quartzites. ## Mineral Associations This mineral most often coexists with braunite, hollandite, quartz, piemontite, shattuckite, and tenorite. ## Localities The most important localities, including the type locality, are in Greece on Andros Island (Myli and Ochi mines). Its occurrence has also been confirmed in the Apuan Alps in Italy and in several places in Japan (e.g., in Kōchi Prefecture).
Rarity
Very rare
For collectors
## Quality Criteria The quality of collectible specimens of this micromineral is assessed based on the abundance of its occurrence on the rock matrix, the certainty of identification (preferably analytically confirmed), and the attractiveness of associated minerals. Grain size, although always small, is also important. ## Popular Localities Specimens from the type locality in Greece are most valued by collectors. Material from other confirmed localities is also sought after by specialized micromineral collectors.
Care and storage
## Cleaning Specimens should be cleaned very carefully, preferably with a soft brush dry to remove dust. If necessary, distilled water can be used, and then the specimen should be thoroughly dried. It usually occurs in such small grains that cleaning is not necessary. ## What to Avoid Avoid ultrasonic cleaners and all chemical agents. Despite its relatively high hardness, the mineral is brittle and should be protected from impacts and abrasion. ## Storage The best way to store it is to place the specimen in a sealed "micromount" box, which protects it from dust and mechanical damage. Store in a dry place.